Paul A. Karger

Transcription

1 Privacy and Security Threat Analysis of the Federal Employee Personal Identity Verification (PIV) Program Paul A. Karger

2 Outline Identify specific problem with FIPS 201 Problem of multiple authentication protocol options Recommend use of single, formally proven secure, standards-based authentication protocol

3 Homeland Security Presidential Directive 12 HSPD 12 August 2004 Government-wide standard for identification of Federal Employees and Contractors Primarily for access to federal buildings, world-wide Must be secure and reliable NIST developed Federal Information Processing Standard (FIPS) 201 Plus series of accompanying documents Two kinds of cards PIV I and PIV II PIV I is for quick deployment for single agencies PIV II is for inter-agency interoperability focus of this talk

4 What is Secure and Reliable Identification? Strongly resistant to identity fraud, tampering, counterfeiting, and terrorist exploitation Can be rapidly authenticated electronically Strong criteria for verifying employee s identity Issued only by accredited providers

5 Contact and Contactless Smart Cards FIPS 201 requires dual-interface smart cards Contact cards must be inserted into a reader provide better security Contactless cards communicate via radio frequencies and therefore could be intercepted Contactless smart cards are similar to RFID tags, but use different standards and have more powerful computational abilities Contactless smart cards receive broadcast power from the reader and have no batteries RF transmissions can be intercepted Reports of successful interceptions at distances from 9 to 50 meters. Interception is MUCH easier when the card is in use and powered by a legitimate reader Therefore, encryption is essential for security, but FIPS 201 does not require encryption over the contactless interface

6 Card Holder Unique ID (CHUID) CHUID evolved from an earlier DoD working group (SEIWG-12) that included a social security account number (SSAN) as part of the unique ID of a card holder DoD puts the SSAN on all military IDs Due to potential identity theft problems, the newer CHUID strongly discourages the use of SSAN CHUID includes a number of other fields including an agency code that identifies for which federal agency the card holder works

7 CHUID transmitted in cleartext FIPS 201 explicitly declares that reading the CHUID is not a privileged operation, and therefore need not be encrypted Agency code (part of CHUID) is sensitive information Very fine grained code 12K3 = Animal and Plant Health Inspection Service 571A = Air Force Command and Control (C2) & Intelligence, Surveillance and Reconnaissance This level of detail could be of great interest to an eavesdropper, and could put federal employees in danger

8 Attack Scenarios Using Agency Code Espionage agents Select individuals likely to have high security clearances to recruit as spies Terrorists Select individuals to target for kidnapping or assassination Encryption could NOT prevent identification if terrorist gets physical access to the ID card, as in TWA 847 hijacking Encryption could interfere with attempt by terrorists to select particular targets off the street, as in the DC sniper case Journalists Identify Valerie Plame as a CIA employee just by remotely reading her FIPS 201 card

9 Outline Identify specific problem with FIPS 201 Problem of multiple authentication protocol options Recommend use of single, formally proven secure, standards-based authentication protocol

10 Usability Issues For cardholder, usability is excellent Contactless smart cards merely need to be waved near the readers For agency developers, usability is not good FIPS 201 is supposed to provide inter-agency interoperability, but it offers many options for authentication that will make interoperability difficult Furthermore, it assumes that each agency can make good security choices, yet it is well-known that selecting appropriate wireless security protocols is very difficult Each agency will choose its own card vendors

11 Recommendation Even if just one agency s cards are broken, there could be serious problems for the employees Require a single, proven to be secure, authentication protocol for ALL agencies Assures interoperability Removes agency need to have in-house cryptographic experts IBM has developed such a protocol and offered it to various standardization bodies Caernarvon authentication protocol

12 Outline Identify specific problem with FIPS 201 Problem of multiple authentication protocol options Recommend use of single, formally proven secure, standards-based authentication protocol

13 Caernarvon Castle North Wales

14 Privacy Preserving Protocol Based on SIGMA (SIGn and Mac) family of protocols, including IKE Part of IPSEC Formally proven SIGMA protocols better protect privacy Key is negotiated before any identities are exchanged Once key is agreed upon, all further communications are encrypted Caernarvon protocol Requires that the reader authenticate first, then the card Underlying protocol is symmetric, but someone has to go first Needs for privacy are NOT symmetric Once the reader has authenticated, the card can make a security policy determination of whether to reveal the card holder s identify SOUPS 2006

15 Non-Mathematical Summary of Protocol First, the reader and the card negotiate a Diffie-Hellman session key This provides cryptographic privacy for all subsequent messages No authentication has taken place yet neither the reader nor the card knows who is on the other end they only know that eavesdroppers have been excluded Second, the reader authenticates itself to the card Third, to protect the privacy of the card holder, the card now decides whether this particular reader is authorized Only if the reader is authorized, the card finally reveals the card holder s identity, so that the reader can decide whether the card holder is to be allowed access. SOUPS 2006

16 Standards Process IBM has submitted the Caernarvon Authentication Protocol for international standardization as part of the European Electronic Signature effort IBM has not asserted IP rights over the protocol Based on existing IKE standards in IPSEC Part of a draft CEN standard When completed, the CEN standard will be submitted to ISO SOUPS 2006

17 Conclusions Problem: FIPS 201 has weaknesses CHUID is transmitted unencrypted putting card holder safety at risk Inter-agency interoperability will be difficult to achieve Each agency has to make difficult security trade-offs without good guidance Problem: Does this meet HSPD-12? Is it strongly resistant to identity fraud, tampering, counterfeiting, and terrorist exploitation? Solution: Fix the next version of FIPS 201 by mandating a formally proven, standards-compliant, privacy-preserving protocol for ALL cards Solution: Limit use to PIV I (no interagency authentication) for now SOUPS 2006

18 Backup Slides Mathematical summary of the protocol SOUPS 2006

19 Algorithms Protocol can use elliptic curves and AES algorithms Examples that follow use regular Diffie-Hellman, RSA signatures, and triple DES, because our first prototype smart card chip only supported those algorithms SOUPS 2006

20 Privacy Preserving Protocol 1 Simple Diffie-Hellman A chooses a random number a with 1 a q-1, computes a key token K A = g a mod p, and transmits it to B. A K A B B chooses a random number b with 1 b q-1, computes a key token K B = g b mod p, and transmits it to A. A K B Neither A nor B has revealed his identity. They now can compute a mutual key K AB, as in simple Diffie-Hellman, and then derive encrypting and message authentication keys, K ENC and K MAC Since we have a session key, the rest of the protocol is protected from third-party eavesdroppers. B SOUPS 2006

21 Privacy Preserving Protocol 2 Reader Proves Identity A sends its certificate to B by encrypting it with K ENC. A computes: E 01 = 3DES KENC (Cert(A)) A B responds with a challenge E 01 MAC KMAC (E 01 ) B A RND.B A now computes: E 1 = 3DES KENC (A Sig SKA [K A A RND.B K B DH(g p q)]) Diffie-Hellman key parameters are included to provide their authenticity B A E 1 MAC KMAC (E 1 ) B SOUPS 2006

22 Access Control Decisions At this point, the smart card can check the reader s identity, and make a policy decision about the reader. Any security policy could be implemented here Even no policy at all SOUPS 2006

23 Privacy Preserving Protocol 3 Card Proves Identity B sends its certificate to A by encrypting it with K ENC. B computes: E 02 = 3DES KENC (Cert(B)) A A responds with a challenge A E 02 MAC KMAC (E 02 ) RND.A B now computes: E 2 = 3DES KENC (B Sig SKB [K B B RND.A K A ]) B B A E 2 MAC KMAC (E 2 ) B Finally, the reader can now verify the card s identity, make its own access control policy decisions and proceed. SOUPS 2006